Alarm system

ABSTRACT

A MODULATED RADIO-FREQUENCY ALARM SYSTEM HAVING A TRANSMITTER AND A RECEIVER IS DISCLOSED. THE TRANSMITTER DRAWS NO POWER UNTIL IT IS TRIGGERED ON BY A SENSOR SWITCH AND AN SCR. WHEN TRIGGERED, THE TRANSMITTER EMITS A RADIO FREQUENCY MODULATED BY AN INTERRUPTED AUDIO FREQUENCY PROVIDED FROM A SIGNAL GENETATOR KEYED BY A MULTIVIBRATOR CODER. A COMPANION RECEIVER INTERCEPTS THE TRANSMITTED SIGNAL WITH A SUPER-REGENERATIVE DETECTOR AND AMPLIFIES THE INTERRUPTED AUDIO TONE TO GIVE A REMOTE INDICATION OF THE TRIGGERING OF THE TRANSMITTER.

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FIPBIO? ALARM SYSTEM CROSS REFERENCF 2 Sheets-Sheet l Original Filed Sept. 10, 1965 N wg INVENTOR GIANNI A. DOTTO mm 3: J mm H mm lllllllll m \o l 4 i i n W B NR I Nw u X j n x\ mm mm H h k l i. 5 8 q m H 8 t ATTORNEY G. A. DOTTO 3,559,195

ALARM SYSTEM 2 Sheets-Sheet 2 ATTORNEY B. Y W W3. M NQ M m. mm

Jan. 26, 1971 Original Filed Sept. 10. 1965 United States Patent 3,559,195 ALARM SYSTEM Gianni A. Dotto, Dayton, Ohio, assignor to P. R. Mallory & Co. Inc., Indianapolis, Ind., a corporation of Delaware Continuation of application Ser. No. 486,498, Sept. 10, 1965. This application Apr. 25, 1969, Ser. No. 820,042 Int. Cl. G08b 3/10 US. Cl. 340-224 1 Claim ABSTRACT OF THE DISCLOSURE A modulated radio-frequency alarm system having a transmitter and a receiver is disclosed. The transmitter draws no power until it is triggered on by a sensor switch and an SCR. When triggered, the transmitter emits a radio frequency modulated by an interrupted audio frequency provided from a signal generator keyed by a multivibrator coder. A companion receiver intercepts the transmitted signal with a super-regenerative detector and amplifies the interrupted audio tone to give a remote indication of the triggering of the transmitter.

This application is a continuation of application Ser. No. 486,498, filed Sept. 10, 1965, now abandoned.

The present invention relates generally to alarm systems and more particularly to the means and method for providing a solid state transmitter and receiver for indicating an alarm.

There exists a need for an all purpose alarm system that is versatile, small, lightweight, reliable and economical. Accordingly, the present invention provides a novel and practical means for meeting the abovementioned requirements.

There is presented, herein, an alarm system that is versatile in that it can be installed in an automobile, in a safe, in a building, beside a bank tellers window, or in any area to be protected. Also, the alarm system of the present invention can be installed in the brief case of a bank messenger or any person required to carry valuables. The alarm system of the present invention can be adapted to detect a fire and indicate an alarm as well as to detect an intruder.

The alarm system of the present invention is small and lightweight since it is to be constructed of transistors and diodes coupled with discrete resistors, capacitors, inductors and transformers. Since it is a transistorized system, there is no appreciable warmup required and the alarm system transmitter can indicate an alarm as soon as it is triggered. The battery, which is the direct current power supply for the transmitter of the alarm system, can be rather small since it is only required to provide power when the alarm system is triggered. The feature of energizing the transmitter only when the alarm system is triggered is a novel feature.

The reliability of the alarm system of the present invention is achieved by the use of reliable electronic components and by the fact that there are no moving parts which can fail to function.

The present invention is an economical approach to providing an alarm system for two reasons. First, the electronic components used in the circuitry are standard components which can be purchased for reasonably low prices. Second, a degree of economy can be achieved by the fact that a single alarm system can be adapted for a wide variety of applications. Likewise, a single receiver can be used with a plurality of transmitters to protect several automobiles, buildings, etc. Each transmitter would be selectively preset to provide a coded signal representing a particular transmitter.

3,559,195 Patented Jan. 26, 1971 ice It is an object, therefore, of the present invention to provide a versatile, small, lightweight, reliable and economical alarm system.

Still another object of the present invention is to provide a solid state transmitter and receiver circuit for a remote alarm system.

Still another object of the present invention is to provide a transmitter for an alarm system which has a solid state circuit means for interrupting the power output of said transmitter so as to provide a controlled frequency output representative of said alarm system.

Still another object of the present invention is to provide a transmitter for an alarm system which is not energized until the alarm system is triggered.

Still another objective of the present invention is to provide a triggering means for an alarm system which will couple the transmitter portion of said alarm system to a direct current power supply.

The present invention, in another of its aspects, relates to novel features of the instrumentalities described herein for teaching the principal object of the invention and to the novel principles employed in the instrumentalities whether or not these features and principles may be used in the said object and/or in the said field.

Other objects of the invention and the nature thereof will become apparent from the following description considered in conjunction with the accompanying drawing and wherein like reference numbers describe elements of similar function therein and wherein the scope of the invention is determined rather from the dependent claim.

For illustrative purposes, the invention Wlll be described in conjunction with the accompanying drawing in which:

FIG. 1 is a schematic of the transmitter portion of the alarm system.

H6. 2 is a schematic of the receiver portion of the alarm system.

- Generally speaking, the present invention is an alarm system comprising, a transmitter portion and a receiver portion, said transmitter portion having a coder circuit for providing a controlled frequency output representing said alarm system, a signal generator circuit responsive to said controlled frequency output so as to develop an audio signal, a means for amplifying said audio signal, an oscillator-output circuit for developing a radio frequency signal which is modulated by said audio signal, an antenna means for transmitting said radio frequency signal, a means for triggering said alarm system so as to energize said transmitter portion, said receiver portion having an antenna means for receiving-"said radio frequency signal which is generated by said 'transmitter portions, a means for developing a second audio-signal which is proportional in frequency and amplitude to said audio signal which modulates said radio frequency signal, a means for amplifying said second audio signal; and a speaker means for indicating that said alarm'system has been triggered.

Referring now to the drawing, and particularly to the schematic of FIG. 1, the component parts of the alarm system and their function can be visualized in conjunction with the following description. The coder circuit 10 is a simplified solid state multivibrator comprising a NPN transistor 11, a PNP transistor 12, a resistor 13, a resistor 14, and a series resistor IS-capacitor 16 network. Transistor 11 functions to drive either positive or negative to the base of transistor 12, thereby causing transistor 12 to switch on and off the power to the signal generator circuit 17 at a frequency determined by the time constant of the resistor IS-capacitor 16 network. Resistor 13 couples the collector of transistor 11 to the base of transistor 12 and resistor 14 couples the emitter of transistor 12 to the base of transistor 11. v

The signal generator circuit 17 comprises a unijunction transistor 18, capacitor 19, resistor 20, resistor 21, capacitor 22, resistor 23, resistor 24, resistor 25, diode 26, PNP transistor 27, transformer 28, capacitor 29 and speaker 30. When the power is turned on by the coder circuit 10, capacitor 19 is charged through resistor 20 to a value that will trigger unijunction transistor 18. When the unijunction transistor 18 is triggered, a positive signal is applied to the base of transistor 27 through capacitor 22, so as to cause transistor 27 to conduct. 'When transistor 27 conducts, a signal is applied to-thejtank circuit formed by a coil of transformer 28 and capacitor 29 to develop the frequency of the signal generator circuit 17. Also, the frequency of the signal generator circuit 17 can be controlled or changed by changing the size of the capacitor 19 and resistor 20. The output of the tank circuit formed by a coil of transformer 28 and capacitor 29 is coupled to the transformer 32 of the transmitter circuit 31 and the speaker 30. Speaker 30 is optional to the alarm system and can be used if an audible signal is desired.

The secondary coil of transformer 32 is coupled to the base of transistor 33 which is the semiconductor element in the amplifier comprised of transistor 33, resistors 34, 35, 40, and 70 and capacitors 36, 37, 38, and 39. The collector of transistor 33 is coupled to the base of transistor 41 through capacitor 42. Transistor 41 is the semiconductive element in the amplifier comprised of transistor 41, resistors 43, 44 and 45 and capacitors 46 and 47. Capacitor 48 couples transformers 32 and 49 to ground. Thus, we have shown a two stage amplifier circuit for amplifying the audio signal developed by the signal generator circuit 17.

The primary coil of transformer 49 is coupled to the oscillator-output stage 50 of the transmitter circuit 31. The oscillator-output stage 50 is comprised of a transistor 51, resistor 52, capacitor 53, resistor 54, capacitor 55, crystal 56, resistor 57, capacitor 58, capacitor 59 and transformer 60. A series network comprised of a capacitor 61 and inductor 62 couples antenna 63 to transformer 60. A coil of transformer 60 and capacitor 55 form a tank circuit for the oscillator-output stage 50. The crystal 56 determines the operating frequency of the transmitter circuit 31 and the capacitor 58 regulates the amount of drive that is applied from the crystal 56 to the base of transistor 51. The signal from transformer 49 is applied to the base of transistor 51 through the voltage divider formed by resistors 52 and 57. Resistor 54 and capacitor 53 are coupled to the emitter of transistor 51 so as to stabilize the transmitter circuit 31.

The power-triggering circuit 64 is comprised of a silicon controlled rectifier 65, battery or direct current power supply 66, resistor 67, and actuating switch 68. The cathode of the silicon controlled rectifier 65 is coupled to the negative side of battery 66 and the positive side of battery 66 is coupled to ground. The anode of silicon controlled rectifier 65 is coupled to a manual switch 69 which couples the power-triggering circuit 64 to the transmitter circuit 31, signal generator circuit 17, and the coder circuit 10. Resistor 67 is coupled between the anode of silicon controlled rectifier 65 and one contact of the actuating switch, the other contact of said actuating switch being connected to the gate electrode of said silicon controlled rectifier.

Referring now to FIG. 2, we see a schematic of the receiver portion of the alarm system. An antenna 73 is coupled to a tap on'a' receiver coil 76 by a loading coil 74 and capacitor 75. Capacitor 75 functions to minimize capacitive loading of the receiver by the antenna 73, and reduces radiation from the receiver. A capacitor 77 is in parallel with the adjustable receiver coil 76 to form a tank circuit for setting the frequency of the receiver circuit. Capacitor 78 is the RF ground for the tank circuit formed by capacitor 77 and receiver coil 76. The tap on the adjustablereceiver coil 76 is coupled to the collector of transistor 79. Transistor 79 is the semiconductor element 4. of the superregenerative detector circuit 72 comprised of transistor 79, capacitors 80, 83 and 86, resistors 82, 84 and 85, and inductor 81. The superregenerative detector circuit 72 operation is similar to that of an audio amplifier. The detector circuit 72 is made to oscillate by feeding part of its output signal back into the input. The feedback, which is accomplished by capacitor coupled between the collector and emitter of transistor 79, causes oscillation at a frequency determined by the tank circuit formed by receiving coil 76 and capacitor 77. The time constant of the resistor-capacitor network formed by adjustable resistor 84, resistor 85, and capacitor 86 in the base circuit of transistor 79, is the regeneration control for the detector circuit 72. When properly set, the resistor-capacitor network in the base of transistor 79 will allow the detector circuit 72 to oscillate to the point of saturation and then stop oscillating for a period of time, after which the cycle is repeated. The rate at which the detector circuit 72 starts and stops oscillating is usually referred to as the quench frequency. The signal that is developed at the quench frequency is an audio signal that is proportional in frequency and amplitude to the modulation of the radio frequency signal received by antenna 73. The signal developed by the detector circuit is applied to the primary coil of transformer 88. Adjustable resistor 87 functions to determine the level of the signal that is applied to transformer 88. The secondary coil of transformer 88 is coupled to the base of transistor 89 which is the semiconductor element of the amplifier comprised of transistor 89, capacitors 90, 92 and 93, and resistors 91 and 94. Resistor 96 couples the secondary coil of transformer 88 to the negative side of battery 99 and resistor 97 and capacitor 98 couples said secondary coil to ground. The collector of transistor 89 is coupled through a capacitor 100 to the base of transistor 101. Transistor 101 is the semiconductor element of an amplifier stage comprised of transistor 101, resistor 102, resistor 103, capacitor 104 and capacitor 105. The collector of transistor 101 is coupled to the primary coil of transformer 106 and through said primary coil to the negative side of battery 99. A speaker 107 is coupled to the secondary coil of transformer 106. A manual switch 109 connects the battery 99 to the balance of the receiver circuit.

The speaker 107 is a means for indicating that the alarm system has been triggered or operated. It is obvious that a flashing light or another indicating device could be used. The manual switch 109 is a means for energizing the receiver circuit so as to receive a signal generated by the transmitter circuit 31 of the alarm system.

Referring again to FIG. 1, the manual switch 110 is an alternate switch to actuating switch 68 and could bemsed by a bank teller or messenger to manually actuate the alarm system. The actuating switch 68 can be a mercury switch which is actuated by movement of a car or safe being protected by the alarm system. Also, the actuating switch 68 can be a switch which is actuated by heat so as to produce a fire alarm. Because the actuating switch can take so many forms, it will be referred to as a means for triggering the alarm system so as to energize the transmitter portion or a means for coupling the transmitter circuit, coder circuit, signal generator circuit, and amplifier circuit to a power supply.

With the above description of components and functions in mind, and by making reference to the drawing figures, the following analysis of operation will serve to convey the functional details of the alarm system of the present invention. The entire transmitter portion of the alarm system shown in FIG. 1 will be installed in an automobile, safe, building, or area to be protected. For illustrative purposes, we can assume that an automobile is being protected. The person leaving the car would close switch 69 to connect the battery 66 to the balance of the transmitter circuit. If a thief were'to open the car doors or start the car, the necessary movement would cause the actuating switch 68 to connect the 'gate'electrode of silicon controlled rectifier 65 to resistor 67, thereby firing said silicon controlled rectifier. When the silicon controlled rectifier 65 is fired, current can flow from battery 66 to energize the coder circuit 10, signal generator circuit 17, and transmitter circuit 31. Since all of the sin cuitry of this invention is solid state, warmup is not required and transmission of an alarm can begin immediately. The coder circuit 10, when energized by battery 66, provides a controlled frequency output to the signal gen erator circuit 17. The coder circuit is a means for establishing a coded transmission or a transmission which can be easily identified. This is accomplished by changing the values of resistor and capacitor 16 so as to develop different time constants fOr interrupting the power to the signal generator circuit 17.

The signal generator circuit 17 responds to the output of the coder circuit 10 so as to develop an audio signal. This audio signal is amplified by the transmitter circuit 31 to modulate a radio frequency signal developed by the oscillator-output circuit 50 for transmission to the receiver portion of the alarm system.

Referring now to FIG. 2, we can discuss the operation of the receiver circuit of the alarm system. When manual switch 109 is closed, the receiver circuit is energized to receive a signal from the transmitter circuit 31. The signal is received by the antenna 73 and applied through loading coil 74 and capacitor 75 to the tap on receiver coil 76. The receiver frequency is set by adjusting receiver coil 76 which forms a tank circuit with capacitor 77. The input to the receiver circuit is also applied to the detector circ-uit 72 which develops an audio signal that is proportional in frequency and amplitude to the modulation of the received radio frequency signal. This audio signal is amplified and applied to a speaker 107 which is a means for indicating an alarm. The speaker output will have a heat which is established by the frequency of the coder circuit shown in FIG. 1.

The alarm system of the present invention, as hereinbefore described in one of its embodiments, is merely illustrative and not exhaustive in scope Since many widely different embodiments of the invention may be made without departing from the scope thereof, it is intended that all matter contained in the above description and shown in the accompanying drawing shall be interposed as illustrative and not in a limiting sense.

What is claimed is: 1. An alarm system comprising: (a) a coder circuit, said coder circuit being a means providing a controlled frequencyoutput representing said alarm system, said means comprising a PNP transistor and a NPN transistor, a first resistor coupled between a base of said PNP transistor and a collector of said NPN transistor, a second resistor coupled between an emitter of said PNP transistor and a base of said NPN transistor, a series resistorcapacitor network coupled between a collector of said PNP transistor and a base of said NPN transistor,

(b) a signal generator circuit coupled to said coder circuit, said signal generator circuit being responsive to said controlled frequency output of said coder circuit so as to develop an audio signal,

(c) an amplifier circuit coupled to said signal generator circuit so as to amplify said audio signal,

(d) an oscillator-outputfcircuit coupled to said amplifier circuit, said oscillator-output circuit being a means developing a radio frequency signal which is modulated by said audio signal,

(e) an antenna coupled to said oscillator-output circuit so as to transmit said radio frequency signal,

(f) means triggering said alarm system so as to couple said coder circuit and signal generator circuit and amplifier circuit and oscillator-output circuit to a direct current power supply,

(g) an antenna receiving said radio frequency signal,

(h) a detector circuit coupled to said antenna receiving said radio frequency signal, said detector circuit being a means developing a second audio signal which is proportional in frequency and amplitude to said audio signal which modulates said radio frequency signal,

(i) an amplifier circuit coupled to said detector circuit, said amplifier circuit being a means amplifying said second audio signal, and

(j) means coupled to said amplifier circuit indicating said alarm has been triggered.

References Cited UNITED STATES PATENTS 2,988,708 6/ 1961 Schmidt 340384X 3,176,229 3/ 1965 Pierce 325-X 3,207,987 9/1965 Kiryluk et a1. 325--115X 3,208,061 9/1965 Gervasi et al. 340224 3,319,167 5/1967 Bray et al. 325-l13X 3,328,789 6/ 1967 Pacheco 340-224 3,335,371 8/1967 Yandell 3251 15 DONALD J. YUSKO, Primary Examiner D. L. TRAFTON, Assistant Eitaminer US. Cl. X.R. 

